A media file is used to communicate media information such as graphics or audio either remotely, such as over the Internet, or locally, from a disk drive coupled to a computer system directly or via a local area network. Media files may contain graphics, audio or both as well as information concerning the graphics or audio.
Some media files are capable of communicating graphics as an animated sequence of frames and may include audio as an integrated part of the frames or as a separate file. The conventional .swf file format built using the conventional Flash 5 authoring tool commercially available from Macromedia, Inc. of San Francisco, Calif. is one type of media file that can communicate graphics or audio using multiple frames. Static graphics are placed in each frame and a player such as the conventional Flash 5 player is used to replay the frames. Although the graphics within each frame are static, the player displays each of a sequence of frames for a very short duration defined by the author of the movie, such as approximately 1/12, 1/15 or 1/20 of a second long, so that the sequence appears animated, much like a motion picture is a series of static images contained in frames. An audio portion may be contained within the data structure for each frame of a Flash 5 media file. The audio portion may contain audio to be rendered during playback of the media file.
To build a media file such as a Flash 5 media file, a user uses an authoring tool such as the conventional Flash 5 authoring tool commercially available from Macromedia, Inc. of San Francisco, Calif. The authoring tool takes source images, audio sources and instructions from an author and compiles them into the frames of a swf file according to one or more instructions it receives. If there is more than one source of audio for a frame, the audio from the sources designated for the frame is mixed prior to placing it into the frame to reduce the size of the resulting media file. Because many media files are downloaded from the Internet or otherwise transmitted over a network, limiting the size of the file can decrease the time it takes to download a media file.
There are several file formats in common use. Compressed file formats such as the conventional MP3 file format use a smaller number of bits to represent audio than other non-compressed file formats. Thus, the use of compressed file formats can ensure the audio in a media file is kept to a small size.
Common format file formats such as the conventional WAV file format are not compressed. Common format files utilize a set number of bits per unit of time, and so it is easier to mix together audio files in common file formats than it is to mix audio files in compressed file formats, because the compression of compressed file formats can mean that different portions of the compressed audio file may use a different number of bits per unit of time. Thus, conventional authoring tools such as Flash 4, the predecessor to Flash 5, have required that users provide all source files to be compiled into a .swf media file in a common file format such as WAV so that if multiple sources of audio are to be used in the media file, they may be mixed, and the resulting mixed common format audio file is compressed into a compressed file format prior to placing the mixed audio into the .swf file.
There are several problems with this approach. Compressed format files are widespread, and so there is much available source material in compressed file formats. If the author wishes to use such compressed format source material, because conventional authoring tools such as the Flash 4 player that preceded the Flash 5 player did not accept files from both common and compressed formats, the author was first required to go through a time consuming and inconvenient process of conversion from a compressed format to a common format. Furthermore, if the author only has one source to be added to a media file, the author was required to convert the compressed file to a common format, allowing for the introduction of loss that may be inherent in the file conversion, only to have the file converted back into the original compressed file format by the authoring tool during which compilation of the .swf file, with the potential for additional loss.
What is needed is a method and system that can create media files from common and compressed file formats and does not require conversion for single sources of audio files received in the same format as is used in the media file.